The effect of the tournament format on the odds

by Sportstatist • 22.11.2016 • Comments Off on The effect of the tournament format on the odds

Whether it is the tennis Australian Open or the baseball World Series, the outright odds are the market that number one bettors look at the outset of a competition to assess the strength of the contenders. With the tournament design having a strong impact on the odds, which format favours the underdog and which favours the odds’ leader? Read on to find out.

As a rule of thumb, stronger contenders tend to deliver consistent results at longer tournaments, with shorter tournaments allowing underdogs to cause upsets more often. But how exactly does the tournament format impact the contender’s chances of winning?

David R. Appleton from the University of Newcastle upon Tyne (UK) conducted a statistical study that compares various tournament formats in order to determine the impact of the tournament design on the chances of teams or players winning the championship or first prize in a sports event.

Tournament formats

In soccer leagues, each pair of teams meet twice for one home and one away match, whereas in knock-out competitions, such as the English FA Cup, the teams are usually selected by a random draw for each round. In tennis, we also see the knock-out format but the players are seeded so that the favorites do not clash with each other in the early stages. Here are the five most common tournament formats and the sports in which they are used:

1. The knock-out

The knock-out format, also known as single-elimination tournament, single penetration or sudden death tournaments is a type of elimination tournament where the loser of a match is sent home. A classic example of knock-out competitions is the cup contest in soccer. Out of the big four American sports leagues, only NFL uses this system for all rounds of its postseason.

2. Seeded knock-out

The seeded knock-out format is used to ensure that the strongest players meet at later stages of a competition, leading to higher quality matches and more excitement. For this tournament design to be used an official ranking list is required. This format is widely used in tennis and explains why we do not get to see Djokovic playing against Murray at the early rounds of a Grand Slam.

3. Round robin

In contrast to the knock-out format of a cup competition, in a round robin tournament each team meets all other contestants in turn. Most association soccer leagues in the world, such as the Premier League and La Liga, are organized on a round-robin basis.

4. Best-of-three

A best-of-three format is a head-to-head competition between two players or teams in which one team or player must win two games in order to win the series. In Grand Slams, for example, women play best of three sets, while men’s matches are decided with a best-of-5-sets format.

5. Swiss

The Swiss system is a non-eliminating tournament format with a predetermined number of rounds, but less than in a round-robin tournament. Since each competitor does not play every other, the players or teams meet one-to-one in each round with opponents who have a similar running score.

To win a Swiss tournament, you need to get the highest aggregate points in all rounds. This tournament format is used when there is a large number of competitors, which makes a round-robin impractical.

The first Swiss tournament was a chess tournament in Zurich, hence the name. Other than chess, Swiss systems are used in eSports and Magic: The Gathering.

Which format favours whom

Based on 10,000 simulations, the below table shows the percentage of times that the best player won each style of tournament outright.

Tournament

format

Frequency of favourite winning

(8 players tournament)

Frequency of favourite winning

(16 players tournament)

h*

non-h*

h*

non-h*

Knock-out

27%

58%

19%

51%

Seeded knock-out

30%

62%

22%

56%

Best-of-three

33%

68%

26%

62%

Round robin

31%

61%

30%

62%

Swiss

29%

59%

21%

50%

* h = tournaments where the quality of teams is relatively homogenous, like UEFA Champions League** non-h = tournaments with considerable disparity of ability, such as the English FA Cup

The first thing that becomes evident from the above data is how heavily the favourite’s chances of winning are impacted, as the number of contenders (and therefore the number of matches) decreases.

The best-of-three format has the highest frequency of outright wins for the strongest team or player, while knock-out tournaments tend to give the outsider an edge.

When it comes to comparing the tournament format, the best-of-three format has the highest frequency of outright wins for the strongest team or player. This means it is more tolerant to a single loss, with the winner of the competition likely to have lost several games before winning first place.

On the other end of the spectrum are the knock-out tournaments, where the lowest percentages are found. This should come as no surprise to sports fans familiar with the good, old cliché “It takes a good team to win the league, but you need luck to win the cup.”

The Swiss tournament gives players an equal number of games, but with the best players often finding themselves at a tie for first place, it is often regarded as a less attractive format of competition.

Although best-of-three and robin round tournaments give contenders a fair chance to win a tournament based on their ability, it is worth remembering that many tournaments are also devised to make sure that entrants have a reasonable amount of play or that outsiders get their one chance to shine.

As for bettors, there is one key lesson to take from the above study. If you want to increase your winnings, don’t place another outright bet without paying close attention to the tournament’s format. The offer is there and for now, that’s all.